This invention relates to apparatus for suppressing vibrations in cantilevered accessories for agitated vessels.
It is common practice in the chemical, food and beverage processing industries, among others, to utilize vessels such as polymerizers, reactors, mixers and the like having various accessories extending into a liquid being agitated. Typically, the shaft of the agitator is located at the central vertical axis of the vessel and passes through bearings, seals and the like located at the top of the vessel. The shaft is rotated by a motor mounted outside the vessel. Blades extending from the shaft near the bottom of the vessel agitate the liquid.
In vessels equipped with this type of agitator, the liquid in the vessel tends to rotate or circulate with the agitator. This reduces the relative velocity between the agitator blades and the liquid and the effectiveness of the agitation. As a result, these vessels are frequently provided with baffles that extend into the liquid and hinder its circulation. Various other accessories such as blowing in tubes for introducing gases or liquid into the vessel, sheath tubes for thermometers or thermocouples, and sampling tubes also frequently project into the circulating liquid in the vessel. These accessories are usually cantilevered in the vessel, with one end mounted in the vessel wall and the free end projecting into the liquid. As the circulating liquid flows past these projecting accessories, eddy currents are generated on the down stream side of the accessories. These eddy currents produce periodic forces on the accessories that cause them to vibrate. These vibrations can loosen the accessories and/or cause structural damage.